Referring to FIG. 1, a block diagram of wireless transceiver with respect to the prior art is showed. The transceiver comprises a front-end circuit 10 and a back end circuit, wherein the front-end circuit 10 is used for transmitting and receiving wireless signal, comprising an antenna unit 11, a switch 13, a receiver 171 and a transmitter 173, wherein the receiver 171 and the transmitter 173 are integrated into a single chip 17.
The switch 13 is used for controlling the wireless transceiver to transmit or receive signal. While the front-end circuit 10 is receiving the signal, the switch 13 can switch to “a” terminal, thereby, the antenna unit 11 will be connected to the receiver 171 through the switch 13, accordingly, the receiving signal will be sent to the receiver 171 from the antenna unit 11. Otherwise, while the front-end circuit 10 is transmitting the signal, the switch 13 can switch to “b” terminal, thereby, the antenna unit 11 will be connected to the transmitter 173 through the switch 13, accordingly, the transmitting signal will be sent to the antenna unit 11 from the transmitter 173.
Generally, in order to reduce signal loss due to impedance mismatch, several matching circuits should be applied to the front-end circuit. A first external impedance matching circuit 113 is provided within the antenna unit 11, a second external impedance matching circuit 151 is provided between the antenna unit 11 and the receiver 171, and a third external impedance matching circuit 153 is provided between the antenna unit 11 and the transmitter 173. Therefore, the impedance matching between the antenna unit 11 and the receiver 171 or between the antenna unit 11 and the transmitter 173 can be achieved according to the first external impedance matching circuit 113, the second external impedance matching circuit 151, and the third external impedance matching circuit 153.
Referring to FIG. 2, a block diagram of another wireless transceiver with respect to the prior art is shown. The wireless transceiver comprises a front-end circuit 20 and a back end circuit. The difference between this wireless transceiver and foregoing mentioned wireless transceiver is that the switch 23, receiver 271, and transmitter 273 are integrated into a single chip 27, thereby; a simplified front-end circuit 20 can be achieved. However, the pin count of the chip 27 will be increased accordingly since the switch 23 is integrated within the chip 27. The chip 27 therefore requires additional pins for connecting the terminals of switch 23.
Furthermore, according to the foregoing mentioned front-end circuits 10 and 20, the switches 13 and 23 thereof are used for controlling to receive or transmit signal, as well as, the signal will pass through the switches 13 and 23 during the receiving or transmitting process. However, signal pass through the switches 13 and 23 would causes the signal loss, such that the noise figure will be increased on the process of receiving signal, as well as, the output power will be degraded on the process of transmitting signal, thereby, the front-end circuits 10 and 20 cannot be applied for the wireless transceiver that demands low noise figure or high output power.